Field of the Invention
The invention relates to an arrangement and method for generating object images in a microscope. In particular, a method for mixing pairs of confocal images and different arrangements for fast generation of parallel confocal images and the combination thereof in real time. The method is used for improving contrast and resolution in confocal images. The suggested arrangements point to some possibilities for a meaningful application of the method for image mixing in parallel confocal single-beam or double-beam methods for the generation of highly resolved images in real time for a wide variety of different applications, especially also for material inspection. By combining at least two confocal images, a resolution of the fine structure of the object is achieved in the mixed image. Contrast, lateral resolution and depth resolution are improved in the mixed image of the object to be examined, which can also be a phase object. Further, the method permits the generation of very highly resolved three-dimensional digital images of optical objects to be examined.
Description of the Related Art
The following references may be pertinent to the present invention:
Literature
xe2x80x9cImage Formation in the Scanning Microscope,xe2x80x9d C. J. R. Sheppard, A. Choudhury; Optica Acta, 1977, Vol. 24, No. 10, pages 1051-1073.
Aside from confocal laser scanning microscopes which often only permit a very complicated and lengthy building of the image, arrangements have become established, above all, for scanning an object plane under examination by means of Nipkow disks, or various scanning pinhole arrays (DE P 4035799.6, DE 19627568 A1, 19714221.4) have been suggested for generating confocal images. In addition to typical incident or reflected light arrangements, transmitted light arrangements have also been suggested (DE 4023650 A1) which have not yet been realized technologically. All of these forms of scanner with confocal bundles operating simultaneously (in parallel) have the advantage of fast confocal image formation in real time for high-contrast observation with the naked eye as well as with a camera (WO 92/01965). In this last cited patent, the camera is used as a surface receiver with confocal features through sensitivity control of surface elements; however, the complete image is built very slowly by the required joining together of partial images. Generally, the disadvantages of parallel confocal single-disk scanners are the poor illumination efficiency (low percentage) and limited confocality due to crosstalk effects of the parallel channels. Improvements in the illumination efficiency were achieved in fluorescence applications through the use of combinations of micro-optic components with coincident pinhole arrays (EP 0539691 A2, DE 19627568 A1).
Parallel confocal arrangements have the problem of a highly illuminated image background which is caused by reflections or scattering at the pinhole disk and which can easily cover up the actual image content. In order to reduce the disruptive scattered light influence of an individual Nipkow disk, Xiao and Kino, et al., 1987, suggested an inclined disk with a directed-reflection disk surface whose illumination reflections and back-reflections were masked in a controlled manner. The steps for eliminating interfering light were supplemented in DE 19511937 C2 by optical wedges and rhombic cut splitter elements above a Nipkow disk and therefore by a more thorough elimination of destructive light components in the image bundle. Some of the disturbances of the confocal effect in the main beam path which occur as a result of added elements can be accepted in many applications, but not often in the use of confocal microscopes in applications demanding very high quality, e.g., in microbiology or inspection technology. An enormous improvement in the suppression of false light was achieved by physically separating the confocal elements in illumination from those in confocal observation. Unfortunately, the resulting use of two confocal arrays also caused an intensified sensitivity in the production of the necessary exact conjugation (19714221.4).
In WO 97/31282, a form of masking correction is carried out in confocal images in that a bright-field image is combined with a confocal image by joint exposure on a camera and subsequent subtraction with a pure bright-field image of the same object section. This results in a brighter image on the camera, which, among other things, is supposed to compensate for general deficiencies in illumination of the confocal image to nonconfocal microscope images.
U.S. Pat. No. 5,365,084 describes an arrangement for examining a running strip of web with a TDI sensor for light detection. The use of a CCD array or a TDI sensor for wafer inspection is provided in U.S. Pat. No. 5,264,912.
The primary object of the invention is to increase contrast and resolution of confocally recorded images. This object is met in an arrangement for generating object images in a microscope, comprising means for recording at least two confocal images of the same object with distinguishable optical object information with respect to image pixels and for storing them one after the other, and means for combining the recorded and digitized images in a pixel-exact manner, and for storing the mixed image formed in this way.
The object of the invention is to further improve the contrast and resolution of confocal images with the possibility of fast three-dimensional imaging of transparent objects or surfaces having vertical structure by applying an image mixing method accomplished by means of combining different confocal images of an object section and representing them electronically (in real time). The description relates to the method for mixing confocal images and to different arrangements for fast generation of parallel confocal images and suitable combination thereof in quasi-real time. However, the mixing method is also applicable to any form of confocal images which can image exactly the same object section, e.g., also suitably generated images from laser scanning microscopes. However, within the framework of the present description, parallel confocal embodiment forms are discussed mainly.
Parallel confocal illumination rasters and imaging rasters for fast generation of confocal, electronic images with complete image information are generated and stored for the subsequent image combination using different scanning principles. The total image is built very quickly through the parallel-acting generation of confocal image points in the partial beam paths. The speed of the image composition offers favorable base conditions for the decoupling of thermal or mechanical disturbances (vibrations) during the building of the image. It also offers the possibility of generating a quasi-real time image which also permits process examinations in or on the object under examination. Due to the efficiency of the image formation and the advantageous depth discrimination of the special confocal principle, 3-D images can also be generated and can supply new object information especially with transparent objects (phase objects).
The invention will be described more fully in the following with reference to the schematic drawings.